Question 1

Which nonopioid neurotransmitter is involved in control of pain pathways?&#10;A)Serotonin&#10;B)Enkephalin&#10;C)Dynorphin&#10;D)$\beta$-Endorphin

Accepted Answer

Serotonin is a nonopioid neurotransmitter that plays a role in the control of pain pathways, among other functions. Enkephalin, dynorphin, and beta-endorphin are all opioid peptides involved in pain modulation.

Question 2

In the primary somatosensory cortex (SI):&#10;A)All body parts are represented by equal amounts of cortex.&#10;B)Body parts are represented by an amount of cortex proportional to their surface area.&#10;C)The sensory homunculus has an upright position.&#10;D)Proprioceptive and tactile information are directed to different parts of SI cortex and are examples of the labeled-line principle.

Accepted Answer

The primary somatosensory cortex (SI) represents body parts not by their physical size but by the density of sensory receptors in that part, leading to a distorted representation known as the sensory homunculus, which is not upright. Proprioceptive and tactile information are indeed directed to different parts of the SI cortex, illustrating the labeled-line principle, where specific sensory inputs are processed by distinct neural pathways.

Question 3

A lesion of the dorsal columns would result in:&#10;A)Loss of pain sensation&#10;B)Impaired graphesthesia&#10;C)Loss of ability to localize a tactile stimulus&#10;D)Motor weakness

Accepted Answer

Lesions of the dorsal columns, which carry proprioceptive and tactile information, can result in impaired graphesthesia (the ability to recognize patterns traced on the skin).

Question 4

Fast-adapting type 1 fibers respond to a tactile stimulus by a:&#10;A)Maintained increase in firing rate for the duration of the stimulus&#10;B)Maintained decrease in firing rate for the duration of the stimulus&#10;C)Transient increase in firing rate at the initiation and cessation of the stimulus&#10;D)Transient increase in firing rate at the initiation of the stimulus and a transient decrease in firing rate at its cessation&#10;E)Transient decrease in firing rate at the initiation of the stimulus and a transient increase in firing rate at its cessation

Accepted Answer

Fast-adapting type 1 fibers respond to a tactile stimulus with a transient increase in firing rate at the initiation and cessation of the stimulus. This is because they are sensitive to changes in stimulus intensity, rather than the duration of the stimulus.

Question 5

The main pathway for fine discriminative touch information from the hand to the cerebral cortex includes:&#10;A)Group A-&#946; axons $\rightarrow$ fasciculus cuneatus $\rightarrow$ medial lemniscus $\rightarrow$ ventroposterolateral (VPL)nucleus $\rightarrow$ postcentral gyrus&#10;B)Group C axons $\rightarrow$ fasciculus cuneatus $\rightarrow$ medial lemniscus $\rightarrow$ VPL nucleus $\rightarrow$ postcentral gyrus&#10;C)Group A-&#946; axons $\rightarrow$ fasciculus cuneatus $\rightarrow$ medial lemniscus $\rightarrow$ VPL nucleus $\rightarrow$ precentral gyrus&#10;D)Group C axons $\rightarrow$ fasciculus cuneatus $\rightarrow$ medial lemniscus $\rightarrow$ VPL nucleus $\rightarrow$ precentral gyrus&#10;E)Group A-$\alpha$ axons $\rightarrow$ fasciculus gracilis $\rightarrow$ medial lemniscus $\rightarrow$ VPL nucleus $\rightarrow$ postcentral gyrus

Accepted Answer

The main pathway for fine discriminative touch information from the hand to the cerebral cortex involves Group A-β axons that travel through the fasciculus cuneatus and medial lemniscus to reach the ventroposterolateral (VPL) nucleus and ultimately the postcentral gyrus. This pathway is specific for fine touch information from the upper body, while the fasciculus gracilis and its corresponding pathway are specific for fine touch information from the lower body. Group C axons are associated with pain and temperature sensation, not fine touch. Precentral gyrus is the location of the primary motor cortex, which is responsible for controlling voluntary motor movements, while postcentral gyrus is the location of the primary somatosensory cortex, which receives and processes sensory information from the body.

Question 6

Which of the following sequences represents a pathway for conscious proprioceptive information (kinesthesia)from the lower limb?&#10;A)Dorsal root ganglion cells $\rightarrow$ nucleus dorsalis $\rightarrow$ dorsal spinocerebellar tract $\rightarrow$ superior cerebellar peduncle&#10;B)Clarke's column $\rightarrow$ ventral spinocerebellar tract $\rightarrow$ inferior cerebellar peduncle&#10;C)Dorsal root ganglion cells $\rightarrow$ dorsal spinocerebellar tract $\rightarrow$ nucleus z $\rightarrow$ medial lemniscus $\rightarrow$ VPL nucleus&#10;D)Fasciculus cuneatus $\rightarrow$ internal arcuate fibers $\rightarrow$ medial lemniscus $\rightarrow$ VPL nucleus

Accepted Answer

Conscious proprioceptive information from the lower limb follows the pathway: dorsal root ganglion cells $\rightarrow$ dorsal spinocerebellar tract $\rightarrow$ nucleus z $\rightarrow$ medial lemniscus $\rightarrow$ VPL nucleus.

Question 7

Second pain is mediated by:&#10;A)C fibers and is a sharp,highly localized sensation&#10;B)C fibers and is a dull,poorly localized sensation&#10;C)A-$ \delta $ fibers and is a sharp,highly localized sensation&#10;D)A-$ \delta $ fibers and is a dull,poorly localized sensation

Accepted Answer

Second pain is mediated by C fibers and is a dull, poorly localized sensation.

Question 8

Pain fibers:&#10;A)Are not activated by a mechanical stimulus unless it is painful&#10;B)End in encapsulated receptors&#10;C)Are large-caliber myelinated axons&#10;D)May be activated by multiple classes of stimuli

Accepted Answer

Pain fibers, also known as nociceptors, may be activated by multiple classes of stimuli including thermal, mechanical, and chemical. They are small-caliber and unmyelinated or thinly myelinated axons. They do not end in encapsulated receptors.

Question 9

Pacinian corpuscles are located:&#10;A)Superficially in the dermis and thus have receptive fields with sharp borders&#10;B)Deep in the dermis and thus have receptive fields with sharp borders&#10;C)Superficially in the dermis and thus have receptive fields with poorly defined borders&#10;D)Deep in the dermis and thus have receptive fields with poorly defined borders

Accepted Answer

Pacinian corpuscles are specialized nerve endings located deep in the dermis and in the hypodermis. They are responsible for detecting vibration and pressure, and due to their deep location, they have receptive fields with poorly defined borders.

Question 10

The gate control theory of pain is best described by which of the following statements?&#10;A)Transient receptor potential (TRP)channels are gated by temperature.&#10;B)Activation of low-threshold mechanoreceptors can reduce or block the activity of ascending pain pathways.&#10;C)Gamma aminobutyric acid (GABA)inhibits neurons in the spinal cord.&#10;D)After sensitization,a pain fiber begins responding to nondamaging tactile stimuli.

Accepted Answer

The gate control theory of pain proposes that activation of low-threshold mechanoreceptors can reduce or block the activity of ascending pain pathways. This means that non-painful touch stimuli can inhibit the transmission of pain signals to the brain. Option A is incorrect because it describes temperature-gated ion channels but does not relate to the gate control theory of pain. Option C is incorrect because while GABA can inhibit neurons in the spinal cord, it is not specifically related to the gate control theory of pain. Option D is incorrect because it describes allodynia, a phenomenon where a pain fiber begins responding to non-painful stimuli after sensitization, but does not relate to the gate control theory of pain.

Deck 7: The Somatosensory System